The present invention generally relates to dialysis systems. More specifically, the present invention relates to automated peritoneal dialysis systems. The present invention also relates to methods of performing automated peritoneal dialysis and devices for performing same.
Due to disease, insult or other causes, a person""s renal system can fail. In renal failure of any cause, there are several physiological derangements. The balance of water, minerals and the excretion of daily metabolic load is no longer possible in renal failure. During renal failure, toxic end products of nitrogen metabolism (urea, creatinine, uric acid, and others) can accumulate in blood and tissues.
Kidney failure and reduced kidney function have been treated with dialysis. Dialysis removes waste, toxins and excess water from the body that would otherwise have been removed by normal functioning kidneys. Dialysis treatment for replacement of kidney functions is critical to many people because the treatment is life saving. One who has failed kidneys could not continue to live without replacing at least the filtration functions of the kidneys.
Hemodialysis and peritoneal dialysis are two types of dialysis therapies commonly used to treat loss of kidney function. Hemodialysis treatment utilizes the patient""s blood to remove waste, toxins and excess water from the patient. The patient is connected to a hemodialysis machine and the patient""s blood is pumped through the machine. Catheters are inserted into the patient""s veins and arteries to connect the blood flow to and from the hemodialysis machine. As blood passes through a dialyzer in the hemodialysis machine, the dialyzer removes the waste, toxins and excess water from the patient""s blood and returns the blood back to the patient. A large amount of dialysate, for example about 120 liters, is used to dialyze the blood during a single hemodialysis therapy. The spent dialysate is then discarded. Hemodialysis treatment lasts several hours and is generally performed in a treatment center about three or four times per week.
Peritoneal dialysis utilizes a dialysis solution or xe2x80x9cdialysatexe2x80x9d, which is infused into a patient""s peritoneal cavity through a catheter implanted in the cavity. The dialysate contacts the patient""s peritoneal membrane in the peritoneal cavity. Waste, toxins and excess water pass from the patient""s bloodstream through the peritoneal membrane and into the dialysate. The transfer of waste, toxins, and water from the bloodstream into the dialysate occurs due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. The spent dialysate drains from the patient""s peritoneal cavity and removes the waste, toxins and excess water from the patient. This cycle is repeated.
There are various types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis (xe2x80x9cCAPDxe2x80x9d), automated peritoneal dialysis and continuous flow peritoneal dialysis. CAPD is a manual dialysis treatment, in which the patient connects an implanted catheter to a drain and allows a spent dialysate fluid to drain from the peritoneal cavity. The patient then connects the catheter to a bag of fresh dialysate and manually infuses fresh dialysate through the catheter and into the patient""s peritoneal cavity. The patient disconnects the catheter from the fresh dialysate bag and allows the dialysate to dwell within the cavity to transfer waste, toxins and excess water from the patient""s bloodstream to the dialysate solution. After a dwell period, the patient repeats the manual dialysis procedure.
In CAPD the patient performs several drain, fill, and dwell cycles during the day, for example, about four times per day. Each treatment cycle typically takes about an hour. Manual peritoneal dialysis performed by the patient requires a significant amount of time and effort from the patient. This inconvenient procedure leaves ample room for improvement and therapy enhancements to improve patient quality of life.
Automated peritoneal dialysis (xe2x80x9cAPDxe2x80x9d) is similar to CAPD in that the dialysis treatment includes a drain, fill, and dwell cycle. APD machines, however, automatically perform three to four cycles of peritoneal dialysis treatment, typically overnight while the patient sleeps. The APD machines fluidly connect to an implanted catheter. The APD machines also fluidly connect to a source or bag of fresh dialysate and to a fluid drain.
The APD machines pump fresh dialysate from the dialysate source, through the catheter, into the patient""s peritoneal cavity and allow the dialysate to dwell within the cavity so that the transfer of waste, toxins and excess water from the patient""s bloodstream to the dialysate solution can take place. The APD machines then pump spent dialysate from the peritoneal cavity, though the catheter, to the drain. APD machines are typically computer controlled so that the dialysis treatment occurs automatically when the patient is connected to the dialysis machine, for example, when the patient sleeps. That is, the APD systems automatically and sequentially pump fluid into the peritoneal cavity, allow for a dwell, pump fluid out of the peritoneal cavity and repeat the procedure.
As with the manual process, several drain, fill, and dwell cycles will occur during APD. A xe2x80x9clast fillxe2x80x9d is typically used at the end of APD, which remains in the peritoneal cavity of the patient when the patient disconnects from the dialysis machine for the day. APD frees the patient from having to manually performing the drain, dwell, and fill steps.
However, continuing needs exist to provide improved APD systems. For example, needs exist to provide simplified APD systems that are easier for patients to use and operate. Further, needs exist to provide lower cost APD systems and APD systems which are less costly to operate. Particularly, needs exist to clinically, economically and ergonomically improve known APD systems.
APD systems need to be improved for home use. One common problem with current home systems is that they are susceptible to electrical shock due to xe2x80x9cleakage currentxe2x80x9d. Current that flows from or between conductors insulated from one another and from earth is called xe2x80x9cleakage currentxe2x80x9d. If any conductor is raised to a potential above earth potential, then some current is bound to flow from that conductor to earth. This is true even of conductors that are well insulated from earth, since there is no such thing as perfect insulation or infinite resistance. The amount of current that flows depends on: (i) the potential, (ii) the capacitate reactance between the conductor and earth and (iii) the resistance between the conductor and earth.
For medical equipment, several different leakage currents are defined according to the paths that the leakage currents take. An xe2x80x9cearth leakage currentxe2x80x9d is the current which normally flows in the earth conductor of a protectively earthed piece of equipment. In medical equipment, impedance to earth from an enclosure is normally much lower through a protective earth conductor than it is through the patient. However, if the protective earth conductor becomes open circuited, the patient could be at risk of electrical shock.
xe2x80x9cPatient leakage currentxe2x80x9d is the leakage current that flows through a patient connected to an applied part or parts. It can either flow from the applied parts via the patient to earth or from an external source of high potential via the patient and the applied parts to earth. Other types of leakage currents include xe2x80x9cenclosure leakage currentxe2x80x9d, and xe2x80x9cpatient auxiliary currentxe2x80x9d.
Leakage currents are normally small, however, the amount of current required to produce adverse physiological effects in patients is also small. Accordingly, leakage currents must be limited as much as possible by the design of the equipment and be within safety limits.
Generally, the present invention provides improved dialysis systems and improved methods of performing dialysis. More particularly, the present invention provides systems and methods for performing automated peritoneal dialysis (xe2x80x9cAPDxe2x80x9d). The systems and methods of the present invention automatically provide dialysis therapy by providing dialysis fluid to the patient and draining spent dialysis fluid from the patient.
Also, the systems and methods of the present invention can perform various dialysis therapies. One example of a dialysis therapy which can be performed according to the present invention includes an automatic dialysis fluid exchange of a patient fill, dwell and a patient drain. The dialysis system of the present invention can automatically perform dialysis therapy on a patient, for example, during nighttime while the patient sleeps.
To this end, in an embodiment a dialysis system is provided. The system includes a fluid supply line. A disposable unit is in fluid communication with the fluid supply line. The disposable unit has at least two flexible membranes that bond together at selected locations and to a rigid plastic piece or manifold. The membranes can be single or double layer. One preferred membrane material is described herein. The membranes seal to one another so as to define a fluid pump receptacle and a fluid heating pathway. The membranes and plastic manifold define a number of flexible valve chambers. The disposable unit also fluidly communicates with a patient line and a drain line.
The manifold and other areas of the disposable unit include reduced or tapered edges that provide an area to seal the membranes. The reduced thickness or tapered area requires less heat than the full thickness, which reduces the heat sinking disparity between the thickness of the manifold of the disposable unit and the thinner flexible membranes. The frame of the manifold is bowed or curved to provide rigidity. The frame is also asymmetrical and designed to be placed into the hardware unit in only one direction.
The hardware unit can be manually transported to a patient""s home and opened so that the patient can place a disposable unit therein and closed so that the dialysis unit and the disposable unit cooperatively form a pump chamber that enables dialysis fluid to be pumped to and from the patient. The hardware unit has an enclosure that defines a pump shell, a valve actuator and a heater. The disposable unit is placed in and removed from the enclosure. The fluid pump receptacle of the disposable unit and the shell of the hardware unit form a pump chamber. The pump chamber operates with a pump actuator, which is also located inside the transportable hardware unit.
When packaged, a plurality of tubes extend from the disposable unit. The ends of the tubes have connectors that attach to a single body. The body defines or provides a plurality of tip protectors that hold the tubes in an order according to steps of the therapy. The body is configured to slide into the hardware unit of the system from one direction, so that a patient can readily pull the tubes and connectors from the tip protector organizer.
The tip protector used to house the patient fluid connector includes a hydrophobic filter that allows air but not fluid to escape. This vented tip protector enables the system to be primed without having to perform elevation balancing or controlled fluid metering. The system performs a prime by flowing fluid through the system and into the patient fluid line until the dialysate backs up against the filter, causing a fluid pressure increase, which is sensed by the system. The system then stops the pump.
The hardware unit also provides a controller. The controller includes a plurality of processors, a memory device for each processor and input/output capability. One of the processors coordinates operation of the pump actuator, the valve actuator and the heater with the various stages of dialysate flow, such as the fill, dwell and drain stages. The processor also controls or obtains feedback from a plurality of different types of sensors. The sensors include, among others, a capacitance fluid volume sensor, a dialysis fluid temperature sensor, a pressure sensor, a vacuum sensor, an air detection sensor and a mechanical positioning sensor.
In an embodiment, the system uses both preset motion control and adaptive pressure control to control the pressure of fluid within the pump receptacle. The system uses a preset pump motor acceleration to overcome system compliance (i.e., membrane and tubing expansion), which would not otherwise be readily overcome by known proportional, differential or integral control. After the system overcomes compliance, the system converts to an adaptive control using adaptive techniques for controlling pressure by precisely controlling the velocity of a pump motor shaft. The adaptive parameters are modified over time to fine tune the system. This method is especially important for the patient fill and drain cycles, wherein the patient can feel pressure fluctuations. The method also readily compensates for pressure variations due to bag height, bag fullness, etc.
The capacitance fluid volume sensor indicates a volume of fluid in the pump chamber, wherein the sensor generates a voltage signal that is indicative of the volume of fluid in the receptacle. The controller receives the voltage signal and converts the signal into an amount of fluid or an amount of air within the flexible fluid receptacle of the pump chamber.
The pump actuator can be mechanically or pneumatically operated. When mechanically driven, a pump motor drives a vacuum source, such as a piston-cylinder, which pulls a vacuum on the membranes of the fluid receptacle of the disposable unit. Here, a mechanical positioning sensor, such as an encoder, senses the angle of a pump motor shaft relative to a home position and sends a signal to the controller, wherein the controller can adjust the pump motor accordingly. The encoder also provides safety feedback to the controller, whereby the controller, once therapy starts, prevents the camshaft from rotating, to a position where the valves free fill the patient. When the pump actuator is pneumatically operated, the system in an embodiment uses a vacuum pump to pull apart the membranes of the fluid receptacle. Here, the system uses a vacuum sensor to sense the state of the vacuum pump and a mechanical sensing device, such as a linear encoder, to sense the state of a pump piston.
Thus, in an embodiment, the system maintains a negative pressure on one of the membranes of the fluid receptacle of the disposable unit to pull same away from the other membrane and draw dialysis fluid into the fluid receptacle. The negative pressure on the active membrane is then released, which pushes the membrane towards the other membrane and dispels the dialysis fluid from the pump receptacle. In another embodiment, a mechanical pump piston can be pneumatically attached to one of the membranes, wherein the system mechanically pulls the membrane away from the other membrane. In an embodiment, the membrane is coupled to the pump piston through negative pressure. The pump also includes a diaphragm that is pulled to a bottom side of the piston head, wherein the membrane is pulled to a top side of same. In a further embodiment, the system mechanically pushes one of the membranes while applying the negative pressure to same.
The system also performs other necessary tasks automatically. For example, the system automatically heats the dialysate to a desired temperature while pumping dialysate to the patient. The heater heats the fluid heating pathway defined by the flexible membranes of the disposable unit. In an embodiment, the heater includes an electrical heating plate. Alternatively, or in addition to the heating plate, the heater includes an infrared heating source. In an embodiment, the fluid heating pathway and the heater define an in-line heater that heats dialysate as it travels from the supply bag to the patient.
The system employs a method of heat control that uses a knowledge-based algorithm and a fuzzy logic based algorithm. The former uses laws of physics, empirical data and sensed inputted signals. The latter inputs a difference between desired and actual temperatures and uses fuzzy logic membership functions and fuzzy logic rules. Each algorithm operates at a different update frequency. Each algorithm outputs a duty cycle, wherein the system weights the fuzzy logic based duty cycle relative to the knowledge based duty cycle and produces an overall heater control duty cycle. This method enables accurate dialysate temperature control.
The system automatically purges air from the dialysate, for example, through the pump chamber. The system also senses a total volume of fluid pumped to the patient, records and logs same. Furthermore, the system knows the instantaneous flow rate and fluid pressure of fluid entering or leaving the patient""s peritoneal cavity.
The disposable unit includes a valve manifold. The manifold defines a plurality of valve chambers. The hardware unit includes a valve actuator that selectively and sequentially presses against one or more of the valve chambers. In an embodiment, a mechanically operated valve actuator includes a single camshaft and a plurality of cams. The cams press against one of the membranes of the disposable unit to engage the other membrane and block or disallow fluid flow. As stated above, the system uses a sensing device, such as a rotary encoder, to sense the angle of the camshaft relative to a home position, so that the controller can rotate the camshaft to open or close one or more valves as desired. The single camshaft toggles back and forth between: supply and pump chamber fill positions; patient drain and system drain positions; and between pump chamber fill and patient fill positions. These positions are actuated by a unique rotational position on an overall cam profile (i.e., the superposition of each of the individual cams as seen from the end of the camshaft).
The disposable unit of the present invention is provided in a variety of different forms. In an embodiment, the portion of the disposable unit forming the heating path is formed by same membranes that seal to the rigid member or manifold that forms the valve chambers. The same membranes also form the pump receptacle. In another embodiment, the disposable unit includes a first set of membranes that form the pump receptacle and the valve manifold via the rigid member. Here, the disposable unit includes a second set of membranes, distinct from the first membranes, which form the fluid heating path. In an embodiment, medical grade tubing connects the first set of membranes to the second set. In particular, the tubing enables the fluid heating path to fluidly connect to the valve manifold.
The disposable unit in another embodiment includes a first flexible membrane and a second flexible membrane that house the pump receptacle, the fluid heating path and the rigid valve manifold. The disposable unit also includes a rigid frame that attaches to at least one of the first and second flexible membranes. The rigid frame enables a patient or operator to place the frame and the disposable unit into the enclosure of the hardware unit of the automated dialysis system. The rigid frame is sized to securely fit into a dedicated place in the enclosure. The rigid frame further holds the disposable unit stable while patient or operator connects tubes to same. For example, the valve manifold provides ports or other types of connectors for connecting to a supply line, a drain line and a patient line. In an embodiment, the rigid frame extends around or circumvents the membranes including the pump receptacle, fluid heating path and valve manifold. In an embodiment, the rigid frame is plastic. In an embodiment, the rigid frame is bowed along at least two sides to increase the rigidly of the disposable unit and to keep the disposable unit from deforming during the heat sealing portion of its manufacture.
In an embodiment, the rigid member or manifold of the disposable unit includes interfaces that allow the membranes to be more easily sealed to the manifold. The manifold edges are tapered to reduce the heat needed to form a cohesive bond between the membranes and the plastic valve manifold. The knife-like tapered edges also reduce or eliminate the gap between the top and bottom membranes, which minimizes the opportunity for leaks to occur in the disposable unit. The chamfered edges also reduce the likelihood that the heat sealing process will bum through the membranes.
The hardware unit described above includes a display device that provides dialysis system information. The display device also enables the patient or operator to enter information and commands into the controller. For example, the display device can include an associated touch screen that enables the patient or operator to initiate automatic flow of the dialysate through the disposable unit. The system begins to pneumatically and/or mechanically pump dialysate through the pump chamber, past the in-line heater and into the patient""s peritoneal cavity. Thereafter, the system automatically runs the other cycles of dialysis therapy, for example, while the patient sleeps and/or at night. The automated system not only transfers dialysate from a supply container to the patient, the system allows the dialysate to dwell inside the patient for an amount of time and automatically operates to transfer the dialysate from the patient to a drain.
The system provides a graphical user interface (xe2x80x9cGUIxe2x80x9d). The GUI in an embodiment employs an embedded web browser and an embedded web server. The web browser and server operate on a main microprocessor for the system. The GUI also employs instrument access and control software, which operates on the main system processor and on one or more delegate processors. The instrument access and control software controls lower level devices, such as the heater and the pump. The GUI also provides intermediate software that allows the web browser to communicate with the instrument access and control software.
The GUI displays a number of therapy set-up screens and a number of dialysis treatment screens. The set-up screens generally walk the patient through the set-up portion of the therapy. The system waits for an operator input before proceeding to the next set-up screen. The set-up screens provide information to the patient in the form of real-life images of the equipment and through animations of the actions needed to connect the system to the patient.
The therapy treatment screens display the various cycles of the therapy to the patient in real-time or substantially in-real time. The therapy treatment screens display information such as cycle time in both a graphical and quantitative manner. The therapy treatment screens do not require input from a patient, who may be sleeping while these screens are displayed. When the therapy is complete, the system once again displays a number of disconnection screens which, like the set-up screens, wait for an input from the patient before performing an action.
The treatment screens are colored and lighted for night time viewing, and may be easily seen from a distance of about ten to fifteen feet, however, the screens are lighted so as not to wake a sleeping patient. In an embodiment, the background of the screens is black, while the graphics are ruby red. In contrast, the set-up screens are lighted and colored for daytime viewing.
With the above embodiments, one advantage of the present invention is to provide improved systems and methods for performing dialysis.
Another advantage of the present invention is to provide improved systems and methods for performing peritoneal dialysis.
A further advantage of the present invention is to provide an automated peritoneal dialysis system and method of operating same.
Still another advantage of the present invention is to provide an automated peritoneal dialysis system that provides dialysis therapy advantages.
Still a further advantage of the present invention is to provide an automated peritoneal dialysis system that has economic advantages.
Yet another advantage of the present invention is to provide an automated peritoneal dialysis system that has quality of life advantages.
A still further advantage of the present invention is to provide a disposable unit having bowed sides, which increase rigidity and decrease flexing of disposable unit.
Moreover, an advantage of the present invention is to provide a disposable unit having tapered interfaces that decrease the heat sinking of the semi-rigid manifold and provide a more robust seal.
Various features and advantages of the present invention can become apparent upon reading this disclosure including the appended claims with reference to the accompanying drawings. The advantages may be desired, but not necessarily required to practice the present invention.